All this material may be referred to for the background but briefly it is in two parts. The first is that considerable interest has been shown in recent years in the use of prostaglandin (PG) precursors in medicine.
For various reasons when raised levels of prostaglandins are required it is not usually practical to administer naturally occurring prostaglandins such as PGE1 and PGE2 to patients. Consequently, considerable attention has focussed on the use of prostaglandin precursors including linolenic acid, gamma-linoleic acid (GLA) and dihomo-gamma-linolenic acid (DGLA).
Conversion of these materials in the body is believed to be as shown in the following diagram: ##STR1##
The broad outline of this pathway is well known, and it brings out clearly that a major function of essential fatty acids (EFAs) is to act as precursors for prostaglandins, 1-series PGs being formed from dihomogamma-linolenic acid (DGLA) and 2-series PGs from arachidonic acid (AA). DGLA and AA are present in food in only small quantities, and the major EFA in food is linoleic acid which is first converted to gamma-linolenic acid (GLA) and then to DGLA and AA, the latter step being irreversible. The conversion of linoleic acid to GLA is a limiting step, adequate in the young and healthy body but often inadequate in ageing or in many diseased states.
DGLA is the key substance. GLA is almost completely and very rapidly converted in the body to DGLA and so for practical purposes the oral administration of DGLA and GLA amounts to the same thing. DGLA can be converted to a storage form, changed to arachidonic acid and thence to PGs of the 2-series, or converted to PGs of the 1-series.
One particular characteristic shown by human and animal cancer cells and by transformed cells is a consistent absence of the enzyme delta-6-desaturase which converts linoleic acid to gamma-linolenic acid. The inventor believes that this fact is of great significance and that faulty essential fatty acid metabolism is a key factor in cancer.
The outline of the pathways of EFA metabolism in the body is as above, and as stated DGLA is the key substance. It can be converted to a storage form, or to PGs of the 1-series, or to arachidonic acid and thence to PGs of the 2-series. The conversion to arachidonic acid is irreversible.
Accordingly, it can be seen that since gamma-linolenic acid is a necessary precursor of dihomo-gamma-linolenic acid and thus of 1-series PGs, and since also cellular stores of DGLA are very limited, cancer cells and transformed cells soon lose the ability to make 1-series PGs and in particular the important compound PGE1.
The inventor believes that many of the characteristic features of transformed and cancer cells are due to this damage to PG metabolism and accordingly that measures used in the treatment of cancer will be more effective, particularly in the long term, if they are supported by measures to restore production of 1-series PGs and particularly PGE1 in the cells.